Cannot boot directly

Recently I did a bunch of changes on my 2-year old PC that has a Intel Quad-core Q6600, Intel DG33FB motherboard, 4GB RAM, etc. Changes included: Repartition the SATA HDD so that I could change it's partitioning scheme from GPT to MBR, re-install Windows 7, install Ubuntu, etc.

Now I have a system that refuses to boot "directly" to the device I select in the BIOS options, be it the HDD, or the CD drive. I *have* to go the BIOS Boot Option menu (by selecting F10 on the BIOS splash screen) and then select the device I want to boot into. How can I fix this?

Some other strange observations: 1. If I let the system boot without pressing F10, it goes on just past the BIOS splash screen till the screen where there is only a blinking cursor on the top-left corner and a hex number (I think it is F8 or something) on the bottom right. Then it freezes there. 2. The BIOS Boot Option menu has 16 instances of "Windows Boot Manager", followed by the HDD and the CD Drive. The options don't go away even if I boot by removing the HDD. Selecting any one instance of WBM brings back the Boot Option menu with one instance of WBM removed ... and so on till all WBM options are gone! 3. I cannot install Ubuntu on the system. The system reboots instantaneously when I start the installation. 4. I have tried re-installing the BIOS update, resetting the CMOS (by removing the battery for >10 mins, setting the jumper to the Reset position). Nothing has helped. 5. If I set the SATA Type to AHCI (rather than IDE), the BIOS splash screen itself does not come up!

Can someone please advise anything else I can try? Thanks a lot in advance!

* I don't have Ubuntu on the system at all - I installed only W7 after re-partitioning.* I have a 100MB NTFS partition that is marked System, Active and Primary. Then there is a 244GB NTFS partition that is marked Boot, Page File, Crash Dump, Primary Partition. Then there is a 54GB block that is Unallocated (I have left this for Ubuntu). I compared this with another (working) PC's partition scheme and found it is OK.* I did an in-place upgrade of W7 - didn't help either.

Basically I think my EFI Boot is broken. Any ideas on how to re-build / fix this? Thanks!

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